Process of separating zinc and lead



v' at .lt atented lltllay it, man

ltl ll lll ll lllt a at t mull lluuill mull W up l i ll anti lElDllll'llJEtlD ltd. Still? 1013B, 01F SALT LAKE ClEltll', U'ltllrlEll.

Itt'o lllratving".

To all whom it may concern:

Be it known that l, lEnWn-nn ll. tlnrnnn, a citieen ot' the United @tates, residing at Salt ltialre City, in the county of Salt Lakeand filtrate ot' lUtah have invented certain new and useful improvements in Processes of in some of the processes of producing lead,

the two metals each acting to render more diilicult the extraction oi each other from the ores. Processes have been proposed here before for separating the two metals, or separately recovering the two metals from such ores, but these processes all have more orless drawbacks.

The present invention is directed to a process in which both the lead and zinc are turned oil from the ore in the term oi compounds, and the turns is so collected that it contains large quantities o'l lead sulfate and nine oxid. This operation may conveniently be accomplished in known manner, tor example by the process olt-lll. Ed. Patent No. l,2'i(i,058 issued to lit. G. ll'llallp The present invention embraces the treatment of the l'ume or bag-house product oi the Hall process, in,v such a Way as to separate, as comdull pletely as possible, the lead tromthe zinc.

ll he bag-house product produced in accord ance With the Hall process consists largely oil lead sultlate and zinc orid. An analysis of a typical example of the said bag-house product is as tollovvs:

Zine onid lhead sulfate Mi r 220% Silica a- 3% @ullur as sulfidemn trace Uther metal oxids, alumina and carbon w. 5%

' salt (sodium chlorid) and in this operation it itpplication filed November at, 1919. fieriaI lilo. 3%,219.

.is essential to get a thorough distribution of the salt through the mass. llt' is advisable to first thoroughly min the materials dry and then to add only a small quantity of Water, after which the product can be dried in suitable manner, and comminuted it desired. The mass is then tled into a furnace in which it is heated in an oxidizing atmosphere to a temperature at which the lead volatilizes in the llOilIl ct chl'orid substantially completely :lrom the mixture, leaving the bulk of the zinc oxidf unchanged. lit will accordingly be obvious that an amount oi sodium chlorid chemically equivalent to the lead present, or in practice an excess of this quantity, should be employed. Under these conditions no substantial quantity of the zinc is chloridized. The lead chlorid begins volatilizing at a temperature at about 750 C, and in order to accomplish the complete volatilization of the lead as chlorid, it is necessary to carry the temperature up to about 1000 to 1100 .tltS above stated, this operation must be conducted in? an oxidizing atmosphere, or else zinc will also be volatilized as chlorid. The lead chlorid tunic is collected from the gases in any suitable manner, tor example, by bag filters, tlottrcll precipitators or in any other known manner, and the lead chlorid thus collected can be converted into pig lead, lead salts, pigments or used for any other desired purposes. Certain other metals Which may also volatilize and may be recovered or separated in known manner.

'lhe' turnaced residue contains zinc oxid quite tree from lead and may be at once reduced to spelter, or employed for various otherpurposes. Einc oxid, which is free "from lead, brings .a considerably higher price than leaded zinc oxid containing the same amount ofzinc.

The heating; and chloridizinr, operation can be carried out in any suitable form of furnace, for example a straight line mechanically or hand rabbled reverberatory furnace canbe used tor this purpose. ll gas is available as fuel, the inullle type roaster similar to those employed for male ing sulfuric acid from zine sulfide ores, can be employed. This type of furnace has the advantage that the products of combustion do not il'llX with the gas carrying the lead chlorid fume, thereby reducting the volume oi gas to vbe handled in the treaters employed for collecting; the lead Fume. in this operabe present in themass will, to some extent, a

tion a small current of air is admitted to the mnflles in order to insure the maintenance of" the oxidizing atmosphere. Any zinc chlorid which is formed during the roasting 7 operation is largely converted back into zinc oxidand chlorme or hydrochloric acid so that ve little of the zinc goes into the lead fume. he amount of zinc lost from the charge during the chloridization operation is ver small, due to the following facts:

I. inc oxid does not decompose sodium chloride to any appreciable extent in a neutral or oxidizing atmosphere at temperatures up to white heat.

II. Zinc chlorid, even if formed in a chloridizing roast, in the presence of air, is largely reconverted into zinc oxid, which is non-volatile.

III.- The zinc in the product goinginto chloridization furnace contains substantially the whole of its zinc in the form of oxid.

IV. The lead in the-bag-house product i I subjected to chloridizat'io'n exists practically entirely in the form of sulfate which salt is capable of reacting with sodium chlorid to form lead chlorid.

1 V. Lead chloride volatilizes readily and without decomposition at temperatures between 750 and 1100 (3., (or better between 800 and 1100 (3.), and can be collected trom the gases substantially quantitatively.

It is to be understood that'sodium chlorid is abovereferred to as being in most localities the cheapest and most convenient halogen salt to employ. In some locations, it

may be advisable to employ other halogen salts of alkali-forming metals, thus calcium chlorid can be employed if desired.

I claim:

1. A process which comprises roasting lead-zinc ore containing sulfur and thereby making a product containing large quantities of lead sulfate andzinc oxid, intimately mixing such product with a chlorid of an alkali-forming metal in amount at least chemically equivalent to the lead compound present in the product, and heating the mass in a non-reducingatmosphere to a temperature between 750 (1., and 1100 (3., whereby the .lead is substantially converted into chlorid and volatilized, and the zinc oxid remains substantially unvolatilized, whereby the lead chlorid may be "collected separately from the zinc oxid.

2. In the treatment of zinc-lead metallurgical-materials, the step of roasting the.

same mixed with a chlorid of an alkali-forming metal, in an oxidizing atmosphere, at a temperature at which the lead will be volatilized as chlorid, while the zinc remains unvolatilized'.

, 3. The process which comprises mixing salt with a metallurgical product containinto oxid, adding a chloride of an alkaliforming metal, heating the mixture"under non-reducing conditions to above 750 C., whereby lead is volatilized substantially without the volatilization of zinc, and collecting the lead fume.

, In testimony whereof I aflix my signature in thepresence of two witnesses.

EDWARD Il. SNYDER.

Witnesses:

OSCAR G. FUNKE, RALPH H. CAMERON. 

